Speakers constitute the least efficient link in a sound reproduction system from the viewpoints of fidelity of the original sound and energy conversion efficiency. Amplifiers and preamplifiers are capable of amplifying input signals at distortion levels that are so minimal as to be substantially incapable of being detected by the human ear and over a frequency range which extends well beyond the range capable of being perceived by the human ear.
The input audio signals so amplified in a substantially distortion-free and noise-free manner (from the point of view of the human ear) are utilized to drive a speaker typically comprised of a low mass cone whose center is driven by a relatively high mass magnetically attractive armature member driven in a reciprocating manner by a magnetic field developed by a coil whose field strength varies in accordance with amplified audio signals. The armature is sluggish due to the moment of inertia resulting from its mass and introduces distortion into the sound generated by the vibrating cone. The conversion efficiency is also low due to the loss in energy which occurs in the conversion of electrical energy into mechanical energy. Electrostatic speakers of the solid state type also suffer from the same disadvantages. Both types of high quality speakers also have complicated designs and are expensive to manufacture.